Solid ink or phase change ink imaging devices, hereinafter called solid ink printers, encompass various imaging devices, such as printers and multi-function devices. These printers offer many advantages over other types of image generating devices, such as laser and aqueous inkjet imaging devices. Solid ink or phase change ink printers conventionally receive ink in a solid form, which is typically a block form known as ink sticks. A color printer typically uses four colors of ink (yellow, cyan, magenta, and black).
The solid ink sticks, hereafter referred to as ink, sticks, or ink sticks, are delivered to a melting device, which is typically coupled to an ink delivery system, commonly referred to as a loader for conversion of the solid ink to a liquid. A typical ink loader includes multiple feed channels, one for each color of ink used in the imaging device. The ink for a particular color is placed in an insertion opening in the feed channel and then either gravity fed or urged by a conveyor or spring loaded pusher along the feed channel toward the melting device. The melting device heats the solid ink impinging on it and melts it into a liquid for delivery to a print head for jetting onto a recording medium or intermediate transfer surface.
The operational speed of solid ink printers has increased in order to produce higher output rates for printed copies. As the output rates have increased so has the demand for melted ink within the printer. In an effort to reduce the melting time for solid ink sticks or pellets, the surface area of an ink stick or pellet that contacts a melting device has been increased. One way of increasing the surface area of solid ink sticks or pellets has been to make the pellets smaller. These smaller pellets, however, are not as easily handled by users as solid ink sticks that are typically the size of a wooden building block or larger. As the pellets approach the size of a small marble, BB, large grain, or the like, they are better stored in containers that can be opened and their contents emptied into a hopper within the machine, for example. Pellets would be stored in a cartridge, which may also be a component of an ink delivery system. One advantage of a cartridge is that ink particulates and smears that can affect ink feed reliability can be mitigated with replacement of the cartridge multiple times over the life of the product.
Solid ink printers significantly differ from ink cartridge or toner printers because they need not be exhausted before additional solid ink is added to the feed channel. Specifically, ink cartridges and toner cartridges should be exhausted before another cartridge is installed so as not to waste ink or toner in a partially emptied cartridge. These cartridges may be typically returned to the manufacturer or other source to be refilled. Solid ink, on the other hand, may be stored on the premises and installed a stick at a time or as a group of pellets. Because the entire solid ink unit is consumed in the printing process, no housing or other component survives for disposal or return to the manufacturer.
The requirement that solid ink remains solid until impinging upon the melting assembly does present some challenges not present in ink cartridge and toner cartridge printers. Because the ink loader is above the ambient room temperature, the ink softens. The softened ink requires more force to be applied to the ink to overcome the increased friction. Additionally, a limit exists for the temperature level in an ink loader in order to prevent the ink from becoming too soft and losing its shape in the loader.
Containers for holding and dispensing solid ink from the ink loader, particularly pelletized solid ink, face some challenges. Traditional containers for pelletized material have been sealed at the time of manufacture such that they are only useful until the material has been dispensed. Once these containers are used, they become environmental waste with which an end-user must contend. Utilizing pelletized solid ink in larger products, such as a tabloid sized printer, is facilitated by employing very large containers and potentially multiple containers for some or all of the colors. These containers would be consistent with the space available in larger imaging products and the generally greater print volume they produce. These large machines are often placed under a lease agreement that includes a process for ink replacement and/or cartridge exchange. Smaller solid ink desk top printers and multi-function printers (MFPs) present a greater challenge in using pelletized ink supplied in cartridges Ink cartridges must not be so large that the purchase price presents an obstacle to users with lower volume demands. The cartridges may have to be replaced prior to being fully depleted to continue printing, as is common to toner cartridges, so some small remaining ink volume may remain in the cartridge when the cartridge is removed from the product for replacement. This ink could easily escape the cartridge through the exit port that enables the ink pellets to enter the ink delivery system. The warm printer environment encourages solid ink to become sticky such that force is usually required for the feeding of the ink. Small cartridges can be designed to be refilled but the present objective of cartridge mechanisms is to ensure reliable, consistent feed and not be prone to disagreeable leakage when removed from the printer. These issues present challenges that previous solutions have not addressed.